This invention relates to a method of separating blood cells components, particularly, to a method of isolating the red cells portion for use in blood component transfusion and biochemical examination.
It was customary in the past to use the whole blood in the blood transfusion therapy. Recently, a so-called "blood component transfusion", namely, the therapy utilizing the transfusion of the required blood component alone, has come to be put into practice in accordance with the progress of medical treatments. However, the blood component transfusion is not extensively employed nowadays because it is difficult to prepare the required blood component in a sufficient amount. In the case of, for example, red cells transfusion, it is difficult to isolate red blood cells substantially free from leukocytes having HL-A type antigens and blood platelets having platelet antigens.
Presently, the following methods of isolating red blood cells are known to the art:
(1) Inverted centrifugation PA1 (2) Washing with physiological saline solution PA1 (3) Sedimentation of red cells using dextrane or hydroxyethyl starch (HES) PA1 (4) passage through a nylon column PA1 (5) Reconstitution of frozen and thawed blood PA1 (1) It is necessary to use a large amount of the adsorbent cotton strings. Specifically, 50g of the adsorbent strings packed at a density of 50 g/300 ml are used for processing 500 ml of the whole blood or red cells suspension. PA1 (2) It is necessary to apply 0.5 to 0.7 kg/cm.sup.2 of pressure for passing the blood through the processing column and about one hour is required for processing 500 ml of blood. PA1 (3) The requirement of high pressure application renders it difficult to use a blood bag made of polyvinylchloride. PA1 (4) The blood platelet removal rate is as low as 20 to 30%, though it is possible to remove 95% of leukocytes. The value of 95% seems reasonably high, but it is necessary to use a large amount of cotton strings for processing a unit volume of blood as mentioned in item (1) above. In other words, the leukocyte adsorption efficiency is not satisfactorily high.
Incidentally, the above-noted methods are described in "Blood Component Therapy" edited by American Association of Blood Banks, Twentieth Century Press, Inc., Chicago, U.S.A., page 9, 1969.
Method (3) noted above is actually employed for preparing leukocyte-poor red cells, but leaves room for improvement with respect to the recovery rate of red cells and removals of leukocytes and blood platelets. In addition, a problem remains unsolved concerning the antigenic property of the sedimentation agent. The other methods are not satisfactory in terms of removal rates of leukocytes and blood platelets.
Further, it is reported in "British Journal of Experimental Pathology, Vol. 7, pp. 281-286, 1926" that Flewing has found adsorption capability of leukocytes on cotton fibers. Based on this finding, Diepenhorst et al have attempted to prepare leukocytes-poor red cells by using medical strings (1 g/m) of cotton fibers as the leukocyte adsorbent, as reported in "Vox Sanguinus, Vol. 23, pp. 308-320, 1972". However, the adsorption method proposed by Diepenhorst et al is not satisfactory in the following:
Still further, U.S. Pat. No. 3,462,361 discloses a method of separating leukocytes from the whole blood by adsorption of leukocytes on synthetic fibers such as nylon and polyesters. However, the method disclosed in this U.S. Pat. is incapable of removing sufficiently the blood platelet and lymphocytes accounting for about 20-30% of the leukocytes by way of adsorption and, thus, unsuitable for isolating the red cells portion alone.